Posted by ed_uk2010 on February 23, 2015, at 12:26:03
In reply to Proper heart precautions with Clozapine, posted by Lamdage22 on February 23, 2015, at 9:10:15
Blood pressure, pulse and temperature will be monitored very frequently when the medication is first started. You will also have several blood tests performed before and during treatment. The most important, and most regular, is the complete blood count. You are likely to have an ECG before starting treatment, and one or more during treatment.
There are several cardiac issues with clozapine:
1. Sinus tachycardia (rapid heart rate) is very common. In most cases it is not serious. Less commonly, it can be caused by one of the more major heart conditions associated with clozapine, such as myocarditis.
2. Blood pressure changes are frequent. Low blood pressure, especially when standing up, is a common occurrence. Dizziness and weakness are symptoms. Raised blood pressure occurs less often.
3. Occasionally, clozapine causes a potentially serious heart condition called myocarditis. This refers to an inflammation of the heart muscle itself. Myocarditis normally happens in the first few weeks after clozapine is started. It is usually reversible if treatment is stopped as soon the diagnosis is suspected.
4. Cardiomyopathy. This is a disorder of the heart muscle which can occur, rarely, during long-term treatment.
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The risk of myocarditis is monitored by looking for symptoms such as increased heart rate + fever, breathlessness and chest pain. Fever, and especially increased heart rate, are common while on clozapine even when there is no myocarditis. Chest pain and breathlessness are much more suggestive of a serious problem. When the diagnosis is in doubt, additional tests are performed to assess for myocarditis.
Additional assessment may be needed in those with persistent and substantial heart rate elevations, normally with a fever, but +/- any cardiac symptoms. The additional tests may include....
1. An ECG to assess heart rate, rhythm and ST depression/elevation.
2. An additional blood count to look for increased or decreased white blood cells (of various types - the differential). A raised eosinophil count is suggestive of myocarditis. A raised white cell count in suggestive of infection/inflammation. A severely decreased white cell count is suggestive of a clozapine-induced blood disorder, with or without infection.
3. Blood tests for CRP (an inflammatory marker) and tropopin (a marker of heart muscle damage). Raised levels of both is highly suggestive of myocarditis. Some doctors monitor CRP and troponin before treatment and then once weekly for around four weeks - to detect myocarditis early. These blood tests can be done at the same time as the regular blood counts.
4. An echocardiogram (ultrasound scan of the heart) to look for signs of abnormal heart muscle movement/function. This is a specialist test.
5. A chest X-ray, mainly if other causes of chest pain and/or fever seem likely eg. pneumonia/infection.
poster:ed_uk2010
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